Km Of Survey Lines Research Articles

An experimental aeromagnetic survey using a rubidium vapor magnetometer attached to the rotary-wings unmanned aerial vehicle

Abstract An unmanned aircraft system (UAS) for aeromagnetic surveying has been developed on the platform of Geoscan-401 rotary-wings unmanned aerial vehicle. The UAS includes a light rubidium vapor magnetometer (RVM) and an additional differential GPS placed on a loop attached to the copter’s body by 50-meter cable. In operation mode, the aerodynamic design of the loop keeps it in a horizontal position. To define the metrological characteristics of the RVM, a series of tests were conducted using the commercially available magnetometers and a calibration test station. On September 2016, two experimental aeromagnetic surveys with the UAS were conducted over an area of 0.7 sq. km located 30 km northward of Saint Petersburg, Russia. Approximately 32 km of survey lines were flown in two flights of 40 minutes each. During the first flight - Survey 1, the UAS was kept at 30 m above the ground surface (altitude 150–165 m), and second - Survey 2 one went at a constant altitude of 160 m (25–40 m above the surface). The variations from the nominal altitude were approximately ± 2 m. The deviation from the line path reaches 10 m for the flights of southward direction because of southwest wind during the survey.

Bet-hedging dry-forest resilience to climate-change threats in the western USA based on historical forest structure

Dry forests are particularly subject to wildfires, insect outbreaks, and droughts that likely will increase with climate change. Efforts to increase resilience of dry forests often focus on removing most small trees to reduce wildfire risk. However, small trees often survive other disturbances and could provide broader forest resilience, but small trees are thought to have been historically rare. We used direct records by land surveyors in the late-1800s along 22,206 km of survey lines in 1.7 million ha of dry forests in the western USA to test this idea. These systematic surveys (45,171 trees) of historical forests reveal that small trees dominated (52-92% of total trees) dry forests. Historical forests also included diverse tree sizes and species, which together provided resilience to several types of disturbances. Current risk to dry forests from insect outbreaks is 5.6 times the risk of higher-severity wildfires, with small trees increasing forest resilience to insect outbreaks. Removal of most small trees to reduce wildfire risk may compromise the bet-hedging resilience, provided by small trees and diverse tree sizes and species, against a broad array of unpredictable future disturbances.

Environmental heterogeneity and species diversity of forest sedges

Summary 1 A field experiment was designed to investigate the relationship between environmental heterogeneity and species diversity in a group of sedges (Cyperaceae: Carex) growing in old‐growth forest. 2 A measure of environmental quality, as perceived by the sedges, was obtained from the survival of clonal ramets of 11 species of Carex planted at 10‐m intervals along each of three 1‐km transect lines. 3 The resident assemblage of sedges was censused along the same three transect lines and along a further 24 km of survey lines in the same forest. 4 The general state of a site was represented by the overall survival of the experimental implants at that site. The general environmental variance between sites provided a measure of environmental heterogeneity. This could be partitioned into a specific variance (mean environmental variance of species) and an environmental covariance. The rate of increase of the general and specific variances with distance between sites reflected environmental structure. 5 The three transects differed in scale. The species diversity of the resident Carex assemblage was correlated with general environmental quality both among and within transects. 6 The three transects differed in structure. The number of resident species, relative to the number expected from the number of individuals sampled, was greatest on the most coarse‐grained transect (steepest increase in general environmental variance with distance). 7 Within each transect, species diversity increased with general environmental variance because the specific correlation of performance (correlation among species of survival in pair‐wise combinations of sites) decreased as the general environmental variance increased. 8 The effect of specific environmental variance was weaker. Overall survival of a species on the transects was not correlated with its abundance in the forest. Neither the transects nor a targeted implant experiment provided evidence for a close relationship between the distribution of species and the state of the environment. 9 As a general explanation of our results, we propose a ‘marginal‐specialist’ model in which the species that dominate the most productive sites also have the broadest ranges, whereas other species are superior in a more restricted range of less productive sites.

A bathymetric reappraisal of Loch Muick, Aberdeenshire

Abstract A new bathymetrical survey of Loch Muick, using a recording echosounder coupled with precision radio position‐fixing incorporates data from a dense traverse network of 54.78 km of survey lines. A detailed chart, contoured at 1 m intervals, and constructed with the aid of a digitiser and computer‐graphics package, reveals many subaqueous landforms. Four ‘morphological provinces’, established on the basis of ridge and basin floor topography are identified. The spatial distribution of features within these provinces concurs with earlier suggestions of Late Glacial activity in the Loch Muick basin. The confluence of the tributary Black Burn glacier with the main Glen Muick glacier and further down‐valley extension of the ice limits are adduced.

The spatially continuous determination of groundwater flow to surface water bodies: Application to the Connecting Channels between Lakes Huron and Erie

The hydrogeophysical method to define the hydraulic properties of the sediments beneath a surface water body described by Taylor and Cherkauer is applied to a specific field site. Collection of electrical resistivity and seismic data long over 200 km of survey lines in the channels connecting Lakes Huron and Erie has allowed definition of the thickness, general composition and hydraulic properties of the sediment column. The geophysics provided a measurement of electrical longitudinal conductance of the sediment column at 40-m intervals along the survey line (> 5000 complete electrical soundings). This parameter has been empirically related to the hydraulic leakance (ratio of the hydraulic conductivity to the thickness of the unconsolidated materials) of the sediment column at discrete calibration points where seepage meters were installed. Groundwater discharges calculated using the geophysically derived hydraulic properties compare very favorably with those calculated directly from the seepage measurements and others calculated independently from analysis of stream gaging records. Convergence of three methods on a single answer is taken to indicate the validity of that answer and to confirm the reliability of the hydrogeophysical approach. The hydrogeophysical approach offers the advantage of higher resolution of lateral variations in hydraulic properties and relatively low monetary and time expenditures when compared with a drilling program. However, it cannot be utilized without calibration to direct hydraulic measurements; it is best run in conjunction with seepage meters and drilling or existing wells. Perhaps its greatest usefulness lies in its ability to rapidly and accurately define locations of high potential for interaction between surface water and groundwater.